[Israel] Keyes, 34, told FBI interrogators that he made several trips to Montreal to sleep with prostitutes. U.S. police arrested Keyes in 2012 for the murder of 18-year-old Samantha Koenig in Alaska.

During FBI interrogations following his arrest, Keyes admitted killing two people in Vermont and hinted that he killed up to 11 people across the U.S., FBI spokesman Eric Gonzalez told QMI Agency.

"But he made a quip that Canadians don't count," Gonzalez said. "It's difficult to know if he was kidding."

And police fear they will never know because Keyes slit his wrists in an Alaskan jail in 2012 awaiting trial for Koenig's murder. American authorities are asking for the U.S. and Canadian public's help in trying to name the unidentified people Keyes is believed to have killed.